Process for the manufacture of cerium-iron-alloy flints



Patented Nov. 24, 1953 PROCESS FOR THE MANUFACTURE OF CERIUM-IRON-ALLOYFLINTS Walter Bungardt, Essen, Germany, assignor to Th. GoldschmidtA.-G., Essen, Germany No Drawing. Application September 21, 1949, SerialNo. 117,069

Claims priority, application Netherlands September 28, 1948 1 Claim. 1

This invention refers to the manufacture of pyrophoric flint material inrod or like shape and has as one of its primary objects to provide meansaffording subjection of an ingot of suitable alloy to an extrusion presshaving a die opening whose cross-section corresponds to that of thefinished flint rod.

Cerium-iron alloy flints are usually made by casting. It has beenproposedto make flints of this kind by the extrusion process which ismore economical than casting. The known attempts in this direction havefailed. It was found that the pyrophoric properties of the alloy werelost during the extrusion process hence the process has been describedin technical literature as completely useless.

The present invention proceeds from the recognition that the diminutionof pyrophoric properties during extrusion is to be attributed to thefact that, on extrusion, the cerium-iron crystals, to which thepyrophoric action of the ceriumiron alloys is to be ascribed, areshattered and that consequently a larger quantity of eutectic matrix isnecessary in order to embed sufficiently the fragments of thecerium-iron crystals so that they are protected against braking out whensubjected to friction by the friction wheel of the lighter. Researcheshave shown that the necessary quantity of eutectic matrix increases withincrease in thesize of the cerium-iron crystals in the ingot introducedinto the extrusion press.

The eutectic matrix has not only the task of embedding the cerium-ironcrystals and protecting them from breaking away, but also of making thepyrophoric properties of the cerium-iron crystals readily excitable. Theeutectic matrix is readily oxidizable, but oxidation manifests itselfnot in spark formation on friction but only in heat production; howeverthis heat production favors the flaming of the pyrophoric crystalfragments. The best cerium-iron alloy for flints produced by castingconsists of about 30 to 40% iron, the remainder cerium. The amount ofeutectic matrix increases with decrease in the iron content.

In the process for the production of pyrophoric films fromcerium-iron-alloys, by means of extruding presses according to thepresent invention, the iron content is therefore lowered to of the totalalloyage. It was shown that with ingots with an iron content lowered tofrom 15 to 25%, when they are produced in a normal manner, such aquantity of eutectic groundmass or matrix is on hand that the fragmentsor fission products of the cerium-iron-crystals result- 2 ing from theextrusion pressing remain suflicient 1y anchored or tied in it. Therequired amount of eutectic groundmass or matrix for the extrusionpressing, is much slighter as the ceriumiron-crystals arecorrespondingly smaller in the ingot used for the extrusion pressing.

The crystals should not be below a minimum size, otherwise they losetheir pyrophoric properties. It has been found, however, that by the useof inoculant additions, i. e. additions resulting in the production ofmore numerous but smaller crystals, or by accelerated cooling of theingot, such a diminution in size of the ceriumiron crystals can beobtained that, on the one hand, the pyrophoric properties are notsubstantially influenced, while, on the other hand, the cerium-ironcrystals can slip past one another during extrusion without shatteringso that an increase in eutectic matrix is not necessary. The

process according to the present invention can therefore be carried outby utilizing cerium-iron alloys with an iron content of more than 25%and up to 40% and an inoculant addition, e. g. zirconium. The amount ofthis addition must not be so large that it substantially aifects thepyrophoric properties of the alloy. Additions of up to 1% zirconium, forexample, are sufficient Particularly advantageous inoculant additionsare such elements that do not form with the other alloying elements anyalloy constituents which are liquid below the extrusion temperature.Alloying constituents which are liquid at the extrusion temperature havea detrimental effect on the extrusion operation.

As the melting point of cerium-iron alloys decreases with reduction inthe iron content, such a reduction has advantages during casting. Itdiminishes, for example, the loss by burning. On the other hand, itdiminishes also the hardness of the alloy so that the friction wheel ofthe lighter rubs more severely against the flint and therefore uses itup more rapidly. If therefore alloys with a low iron content are used inaccordance With the invention, it is useful to add to themhardness-increasing elements, for example tin, magnesium, cadmium orzinc, in a quantity which does not substantially affect the pyrophoricproperties of the alloy.

Where reference has been made above to cerium, this term is intended toinclude the misch metal customary in the trade which, in addition tocerium, is always accompanied by other rare earths, for examplelanthanum. Y

The high oxidizability of the cerium-ironaldestroyed in time byoxidation from the air, in particular under the high temperatures of hotand moist climates. Cerium-iron fiints therefore usually have aprotecting covering. It has now been found that the lastingness -isincreased to an extraordinary degree if the cerium-iron alloy is plungedin oil when in hot condition.

This can easily be effected in the case of ex-- truded flints by leadinginto oil-the rod=of material delivered hot from the extrusion press;with or without an intermediate passage through an atmosphere of inertgas-"which,- forzexample,

may be argon, hydrogen 0rnitrogen: This method of improving thelastingness,.,however,

not limited to extruded "flints.

The lastingness can also be improved in the case of extruded material bysurrounding; the

ingot with a coating metal and then extruding it, so that the emergingrod of cerium-iromalloyj is surrounded by a thin coating of theprotecting metaL- Aluminium. has been found. specially suitablefo'r thispurpose; The ingot "can either belwrapped. with aluminium foil;introduced "into an. aluminium tube,', or'have' aluminium cast aroundittIt'will thusbe recognized' that there'has'been provided, according, tothe invention a novel method 0 f producing pyrophoric' flint materialinrrodpformation which comprises thesteps of preparing an" ingotof'cerium-iron alloy with an ironcontenti'of approximately, 15% to. 25%by weight, and then subjecting said ingot'which is 0 Numbersteps ofepreparing an ingot of cerium-iron alloy with an iron content ofapproximately 15% to 25%3by WeightpandFthen subjecting said ingot, whichis 'devoid of any outer cover, to extrusion under application of heatand pressure, whereby the resultant extruded material is dischargedthrough an extrusion die opening of a cross-section corresponding tothat of the finished flint rod;

WALTER BUNGARDT.

References Cited in-the file of this patent UNITED STATES PATEN'I'S NameDate Welsbach Nov. 22, .1910 Eorcellon Nov. 8,;1921 Winston Dec.-10;,1935 Van Dusen, Jr., et a1. D'ec. 1,-1936 FOREIGN PATENTS Country;Date? Great Britain Feb. 14; 1945 Number:

